Start-stop printer adaptation to synchronous multiplex telegraphy



- Y I E. MATHES v 2,167,247

START-STOP PRINTER ADAPTATION TO SYNCHRONOUS MULTIPLEX TELEGRAPHY Filed Sept. 5, 1957 TAPE TRAMjM/TTER A SPEED CONTROLLED DRIVE MOTOR r0 7J4PE TRANSMITTER 8 7'0 TAPE TRANSM/Z'TER C POWER 3/ AMPLIFIER T 24 TRANSM/ZTER POLE-CHANGING Q- COMMUTATOR 9 l8 LOCK/N6 CIRCUIT {9 SYNC'HRON/ZER FOR MoroxzspEEo CONTROL RAD/0 1 REc /vER 1Z9. 2 I mar-Em PRINTER .4

I I 3 [+8400 CHANNEL! m q 3 INTERL/JCED 7-l/N/7'S/6M4ZS START-STOP- PRINTER C LOCK/N6 CIRCUIT I INVENTOR ,Q/CHARD E. MA THES ATTORNEY Patented July 25, 1939 UNITED STATES PATENT OFFICE START-STOP PRINTER "ADAPTATION T0 SYNCHRONOUS RAPHY MUL'I'IPLEX TELEG- Richard E. mules, Westfleld,-N. 3., 'assignor to Radio Corporationof America, a corporation of Delaware Application September 3, 1937, Serial No. 162,280

8 Claims. (01. 178-522) .various forms of code signalling, including Morse code, and the so-called five-unit printing code. Printers which are adapted for synchronous operation in response to five-unit code signals are of one type. An adaptation of synchronous multiplex telegraphy to the requirements of radio communications is disclosed in my pending ap- -plication Serial No. 101,204, filed September. 17, 1936, which was assigned to the assignee of this application. A somewhat similar adaptation is disclosed in U. S. Patent No. 2,160,463, granted May 30, 1939, to James A. Spencer.

There is another type of printers known 'as start-stop printers which respond usually to signals having seven elements of which one is a start element, five of which are the code selecting elements and the last of which is the stop eler ment. It is anobject of my invention to provide a synchronous multiplex system adapted to operate a start-stop printer.

It is another object of my invention to provide a communications system for use particularly on radio channels wherein the signalling time is successively assigned to different channels and the repetition of assignments thereto is at a. rate sufficient to allot the time to each channel successively and once during the time interval ordinarily allotted to the unit time element 'of a code signal. Thus, for example, if a code signal for a start-stop system consists of seven elemental time units, and if the system is adapted to transmit three messages simultaneously, then each channel will successively occupy the signailing time once for every time unit of the sig-- time unitsjorbauds as they are called; that is,

seven bauds per code signal.

The novelty which Ibelieve to reside in my improved arrangement as herein disclosed resides fundamentally in theadaptation of a start-stop printer system to synchronous multiplex transmission channels. Ordinarily, as has been known in the past, a'start-stop system was used only in simplex circuits, although, of course, it is well.

known how to adapt a simplex system of any type 'to certain forms of duplexing.

my invention, as above mentioned, other objects and advantages will presentlybecome apparent as the detailed description thereof is set forth.

In the following description reference will be made to the accompanying drawing, in which Figure 1 shows diagrammatically the essential elements of construction which go to make up the system as a whole, and Fig. 2 is 'a diagram showing how the transmitting time is allotted successively to different channels so as to-permit of interweaving the elements of different code signals. Itwill be understood, however, that this drawing discloses only one preferred embodiment and that variations from that embodiment may readily suggest themselves to those skilled in the art.

Referring to the drawing, I show a drive motor I, the speed of which is controlled from some convenient synchronizing source or constant speed vibrator. This motor drives a pole-changing commutator 2 whereby direct current of opposing, polarities may be impulsed into a power tion for driving asynchronous motor 4. Other power amplifiers and associated synchronous m0- tors are preferably operated at the same time with operating units 3 and 4 when traffic is to be maintained on the different multiplex channels. In a three-channel multiplex system it is customary to dispose three brushes 24 at 60 angles about the periphery of the pole-changing commutator 2, one for each of three power-arm plifiers 3. For the sake of simplicity the details of construction appropriate to only one channel have been shown in the drawing.

The phasing of each synchronous motor 4 with respect to the others of the multiplex system is readily accomplished with the aid of a strobescope or its equivalent of any preferred type. Such a stroboscope is here shown as constituted by a neon lamp 5 in front of which is a rotating disc 6 having an opening ,1 therein for observing the position of the disc at the instants when the neon lamp 5 is ignited. The device for transmitting impulses to the lamp 5 has not been fulthus lights the lamp 5 for a brief moment. Thus the phasing of the synchronous motor 4 may be fish observed by its fixed relation to the position of the disc opening I when the neon lamp 5 is ignited. The proper phase relations between the ure the signalling time allotted to each channel is shown by the elements 8. It will be seen that the time normally allotted to a code element of the ordinary start-stop simplex system is here divided into three smaller units in order that three separate communications may be transmitted. as by multiplex methods-over three channels simultaneously.

The drive motor i is shown conventionally as connected to a. multiplex distributor 8; as well as to the afore-mentioned pole-changing commutator 2. The multiplex distributor receives plus or minus impulses on each of. its segments for keying a radio transmitter 9. Each code signal, as initiated by a tape transmitter i ii, usually consists of seven elements, the first of which may be considered a marking element if there is no code signal available to be transmitted, and a spacing element if the start impulse is to be transmitted. This start impulse is then followed by the selecting code having five units of either plus or minus polarity according to the permutational arrangement necessary for transmitting a given character. The five-unit selecting code is then followed by a stop impulse as the seventh unit of the signal.

The tape transmitter device It may be of any well known type such that the code selection can take place within the period of time taken up by one revolution of the commutator brush it over the segments of a distributor indicated generally at I2. This distributor may be of the face plate type as shown, or in place thereof a set of cam-actuated contact springs may be'substituted. In either case the commutator is actuated by thesynchronous motor 4. During one revolution of the brush II sevenrevolutions oi the brush 28 are necessary (according to the arrangement shown in the drawing) in order to obtain the transmission of a given code signal as set up by the keyboard or tape transmitter l6. Other tape transmitters B and C will ordinarily be feeding signals through their appropriate com'mutators (like I2) to different segments of the multiplex distributor 8. The elemental portions of the signals are, therefore, interlaced. If desired, the R. P. M. of the brush 23 may be reduced by duplicating the segments on the distributor plate a.

In the commutator 42 the segment allotted to the start impulse is shown at 53. The five segments for the selecting code are designated a, b, c, d and e, respectively, and the stop segment is designated M. Since a positive marking impulse can be adopted for the stop unit of the code signal, the segment I4 is shown connected to the positive side of the source i5.

Each code selecting operation of the transmitter Ill is initiated by a movement of the transfer switch 26 from engagement with a positively polarized contact to a contact through which the collector ring 21 and the channel selecting segment 28 are interconnected. If the perforated tape is temporarily arrested, then segment 28 is continuously fed with marking bias potential. As shown in the aforementioned Spencer U. 8. Patent 2,160,463, the sensing of tape perforations by the pecker pins on the transmitter is suitably timed in relation to the commutator cycles so that no incomplete code signals can be transmitted.

The code-forming switches of the device Ill are conventionally shown with marking contacts onv the right connected to the positive side of the source it and with spacing contacts on the left connected to the negative side of the source l5.

Other details of the device iii are well known in the art and it is unnecessary to make further disclosure of such details in this application, since .they form no part of the invention.

It will be understood, of course, that by means of suitable gear ratios between the motors and the drive shaft connections to each rotary unit, the correct timing of the different commutator brushes in relation to each other will be maintained.

Various forms of tape controlled transmitters are known (and their use is herein contemplated) in which the tape itself determines whether or not the feeding device'shall remain in operation mitter then the transfer switch remains in position tokeep the segment 28 biased with marking potential. On the channel in question, therefore, the receiving printer at the other end of the communications channel will remain inactive. In all respects, therefore, the receiving printer is enabled to function in the same manner as is customary for operation on a. simplex start-stop printer channel. I

In order to complete the disclosure of my invention I have shown a radio transmitter 9 feeding signals to an antenna H from which energy may be radiated to the receiving antenna I8 and utilized thereat in the control of the radio receiver IS. The output signals from the receiver it may be fed to a receiving multiplex distributor having as many segments 2| thereon as there are channels to be multiplexed. Each of the tributor 20 is preferably driven by a synchronousmotor 22, current for which is obtained in the same manner as shown for equivalent synchronous motors 6 at the transmitting station. In this case, however, it is necessary to derive from the signals themselves the synchronizing impulses for maintaining the proper speed of the master drive motor at the receiving station corresponding to the drive motor I at the transmitter. This method of synchronizing is well known in the art and need not be further dwelt upon in this disclosure.

In the operation of my invention it will now be seen that at the transmitting end the perforated tape is scanned by the pecker pins, which mechanically actuate switches of one type or another for impressing plusand minus impulses simultaneously upon the various segments a to e inclusive of the distributor l2. These peckerpin-controlled circuits are then scanned through the medium of the distributor and the resulting impulses are applied to the line through the multiplex distributor 8. The various units of each code signal are transmitted sequentially and Despite the starting and stoppingplurality of printing telegraph transmitting distributors each having time-division positions for each element of a start-stop code signal, additional motors each for individually driving one of said distributors, synchronizing means operable from the first said motor for controlling the speed of said additional motors, means for fixing the speed ratio between said commutator and said distributors, also the mutual phase relationships between the several distributors, thereby to obtain successive channel-time allotments for each element of the respective code signals to be transmitted, independent means .appropriate to each multiplex channel for feeding code signals to one of said distributors, a plurality of start-stop printers respectively operable by signals on each multiplex channel, and means synchronized by said signals for maintaining the proper distribution of said signals to said printers.

2. A system according to claim 1 and further characterized in that the last said means includes a multiplex channel-time receiving commutator operable in'synchronism with the first said commutator.

3. Apparatus for transmitting time division multiplex signals for control of start-stop printers comprising a channel time allotment commutator and a plurality of code-element distributors, means including appropriate code signal keying devices for feeding start-stop character-signals to each of said distributors, connections from each distributor, to respectively different positions on said commutator, individual synchronous motors for driving each of said distributors respectively, and means controlled by the speed of said commutator for regulating the frequency of the alternating current fed to-said motors.

4. Apparatus according to claim 3 and include ingmeans for maintaining constant phase displacements'between respective ones of said distributors while permitting each of said keying devices to be started and stopped independently.

5. In a system for simultaneously operating a plurality of start-stop telegraph printers over a single time-division multiplex communications channel, the method of signaling which comprises dividing the signaling time into unitary elements successive ones of which are utilizable for the operation of diiferent printers, each unitary element constituting an aliquot part of a character code signal, causing independent keying operations to be made for the transmission of equal length character code signals appropriate to each printer, and causing the unitary elements of said code signals to be interlaced when transmitted over said channel.

6. In a system for simultaneously operating a plurality of start-stop telegraph printers over a single time-division multiplex communications channel, the method of signaling which comprises dividing the signal time into unitary elements successive ones of which are utilizable for the operation of diflerent printers, causing diiferent communications to be independently translated into start-stop character code signals of equal length, causing said unitary time elements to be appropriated individually and in -rotation by different portions of diiferentcode signals, thereby to interlace the units of said code signals, and causing the units of each code signal, when received, to be segregated for control of a. character printing operation on one of said printers, respectively.

'7. In a time division multiplex telegraph system, a perforated tape transmitter adapted to control the composition of 5-unit printing telegraph code signals, a commutator having seven time-division positions one of which corresponds with a start unit, five of which cover the units of a 5-unit code signal, and the seventh of which corresponds-with a stop unit of a 7-unit startstop code signal, means for impressing marking and spacing bias potentials on the several positions of said commutator under control of said perforated tape transmitter, means for interlacing the elemental portions of the code signals of diiferent channels in said multiplex system, a

synchronously controlled channel time distributor located at a receiving station in said system, a start-stop printer at said receiving station, and means operative in accordance with the distribution of code signals by said distributor at said receiving station to respectively different channels of the multiplex system for causing saidstart-stop printer to print the intelligence represented by said 7-unit start-stop code signals.

8. In a time division multiplex telegraph system having synchronously controlled distributors at the transmitting and receiving stations respectively, the method of utilizing start-stop printer code signals on at least one of the multiplex channels, which comprises scanning at the transmitting station a 5-unit code record, translating the effects of the scanning operation into a sequence of code impulses of permutationally arranged marking and spacing biases, prefacing each code signal by a start signal of spacing bias, sufiixing each code signal by a stop signal of marking bias, interlacing the seven units, including start, code and stop units, of signals pertaining to one channel with signal units of different channels in the multiplex system, alloeating the 7-unit cede signals thus formed and transmitted to an appropriate time division multiplex channel, and causing intelligence to be printed at the receiving station in accordance with the significance of said 'I-unit code signals.

RICHARD E. MATHES. 

